There is a need for analyte detection that combines the speed and sensitivity of light-based sensors with the high specificity of biomolecular assays such as nucleic acid hybridization assays. In applications ranging from metabolic diagnostics to detection of pathogenic organisms, biomolecules are typically detected through either nucleic acid amplification or antibody recognition. Signaling is usually accomplished by attaching luminescent labels to probes. These conventional tests are typically difficult to multiplex and require equipment that is bulky, intricate and expensive.
A number of systems combine the use of light-based sensors with the use of biomolecular probes. These systems usually involve complex optics to route light to a zone where the probes can interact with the analyte. The cost and complexity renders such systems impractical for routine diagnostics or biohazard monitoring.
Bright et al describe a microsensor array comprising a sensor located in microwells on the top surface of a light emitter, for example, an LED. See Bright et al, U.S. Pat. No. 6,492,182, filed Jul. 28, 2000, issued Dec. 10, 2002, and U.S. application Ser. No. 2003/0027353, filed Sep. 25, 2002, published Feb. 6, 2003. Bright et al disclose a sensor that is physically embedded in sol-gel glass inside the microwells. The sol-gel glass has a surface area of approximately 100 m2/g and pores approximately 0.5–500 nm in diameter. The use of microwells complicates manufacture of the detection device. Moreover, the nano-pores in the glass impede or prevent in-diffusion when the analytes are biomolecules such as nucleic acids.